With the growth of the specialty soap market, consumers are being offered personal washing bars that have a much more hand crafted “one-of a kind” appearance—so called artisan soaps. Technically such bars have several characteristics that contribute to their distinctive appearance: i) sharpness of the boundary between the phases; ii) easily recognizable difference in optical texture and/or pattern that goes beyond color; and iii) a certai degree of bar to bar non-uniformity. Differences in optical texture and pattern are especially important to convey a collection of sensory expectations associated with bar.
To achieve a highly distinctive appearance, artisan soaps have been predominantly made by melt-cast processes—either single casting or sequential multiple casts. For example, U.S. Pat. No. US 2003/0171232-2003 to Freeman et al discloses a decorative soap that contains soap inclusions that are coated with a glitter agent (metallic pigment). The coating makes the soap inclusions resemble a mineral.
Although meltcast processes can yield bars with highly controlled patterns, they are generally slow and labor intensive. Consequently, multiphase artisan soaps are relatively expensive and tend to be confined to upscale specialty shops and outlets. Furthermore, melt-cast soaps are known to have high wear rates and mushing characteristics that make them less preferred for everyday use.
U.S. Pat. No. 6,730,642 to Aronson et al describes an extruded soap into which is dispersed a second phase that is added as solid pieces prior to the final compaction step in billet formation. By controlling the hardness ratio of the two solids, deformation of dispersed phase during extrusion can be minimized thus producing bars with distinctive dispersed inclusions (chunks or bits). Although the process is highly efficient, it has not proved possible to completely eliminate deformation and breakage of the dispersed bits because the composite mass is subject to extensive shear during extrusion.
This deformation during extrusion leads to three problems in connection with fabrication of bars having inclusions. First, the deformation tends to promote the covering of the inclusions by the continuous phase, consequently reducing the number of domains or bits that are distinctly visible at the surface of the freshly made bar.
Secondly, the shear field which deforms the inclusions leads to a “smearing” or “blurring” of the discontinuous domains thus reducing their visual crispness.
Finally, it has so far proved very difficult by previous extrusion processes to control the orientation of the inclusions which tend to be distributed in various orientations within the bar. This problem is especially acute for shaped inclusions designed to have a recognizable shape that would be evident to consumers by cursory visual inspection of the bar, e.g., a flower petal.
Similar problems are encountered with various other processes disclosed in the art to make striped, marbled or variegated soaps wherein multiple phases are combined and subjected to extrusion.
Several publications have addressed this problem. These include:
DE 41 07 445 A1 to Gartner discloses forming a cavity in a body of soap that extends from its surface to its core region and then placing a secondary soap in this cavity.
WO 99/67355 to Fischer discloses a process for the production of multicolored soap involving the insertion of one soap mass into another soap mass of a different color or pattern.
Both U.S. Pat. Nos. 4,318,878 and 4,311,604 to Hornig disclose a soap comprising a primary soap bar body having a cavity designed to receive a secondary soap that is embedded into this cavity.
GB 574, 291 to Slack discloses a soap having a cameo or other artistic feature made by first stamping a white soap with a projection die that creates a recess in the soap. This recess is filled with a second soap and stamped to create the desired relief.
U.S. Pat. No. 4,175,050 to Charduck et al discloses shaped washing agents having a mosaic-like structure made by molding under pressure a mixture of individual colored particles of soap 1-20 mm in size under conditions which remove any occluded gas.
U.S. Pat. No. 3,294,692 to Kelly et al discloses a striped soap bar wherein the bars is made by inserting multiple grooves of differently colored soap utilizing a specially constructed slotted die.
U.S. Pat. No. 5,605,765 to Rudick discloses a decorative composite formed by extruding a plurality of colored rods into a elongated block and then cutting cross-sections that expose the pattern.
DE 1,617,254 to kappus describes a soap bar with strips inlaid in at least one surface wherein a soap pellet is produced with a recess corresponding to the shape of the inclusions (strips) to be inlaid. The inclusions are inserted into this recess starting from the surfaces. The pellets are then cut into tablets and pressed in a form that provides different degrees of compression in different of the form.
The above processes introduce considerable complexity to a conventional soap finishing line in terms of process steps and equipment. Furthermore, they provide only limited flexibility in accommodating different shaped inclusions on the same process line and rapid changeover. Thus, there remains a need for an efficient and flexible high speed processes to make multiphase cleansing bars suitable for mass market that have visually distinctive domains with sharply defined boundaries, which are clearly visible at the surface of the bar, and which can be orientated in a preferred direction.